1. Field of the Invention
The present invention relates generally to optical systems and methods. More particularly, the present invention relates to integrating optical systems and methods.
2. Disclosure of the Related Art
Many devices are assembled using a UV activated adhesive. When UV light of the proper wavelengths and incidence (power per unit area) impinges on the adhesive at the bond line for the proper length of time, the adhesive will harden. The required wavelength band, incidence and time of exposure vary according to the formulation of the particular adhesive used. The time of exposure, in combination with UV incidence, determines the dose (energy per unit area) applied to the object. The required wavelengths are generally polychromatic (broad band), as produced by an arc lamp for example; however, narrow band radiation, as produced by an LED or laser, is sometimes used.
In a typical UV curing application, the required UV incidence on the part can range from a few mW/cm2 to several W/cm2, for example, between 100 mW/cm2 and a 1500 mW/cm2. Generally, incidence is understood as the irradiance incident on a surface. Required wavelengths range from 200 nm to 600 nm, for example, wavelengths between 250 nm and 450 nm are used. Most commonly, wavelengths between 300 nm and 400 nm are used.
Assembled devices generally have a UV cured surface or adhesive extending over complex surfaces. For example, for medical applications, balloons may be glued to catheters used in angioplasty procedures. The balloon is slid over the end of the catheter; glue is applied to the balloon/catheter interface such that the entire cylindrical interface is wetted. This cylindrical surface must then be cured.
Surfaces other than cylindrical are also common, such as bonding a Y- or T-connector to IV (intravenous) tubing. Oftentimes the bond line at the connector/IV tubing interface must be cured by transmitting light thru one of or more of the objects being assembled, as part of the bond line lies on the side of the object opposite the light source.
Some objects require more than one bond line. Catheter balloons, for example, may require a bond at both ends of the balloon, and the bond lines may be separated by one or more centimeters. Several radiomarkers may be assembled on a single catheter, separated by several centimeters. An inline Y- or T-connection in an IV line will have 3 or 4 different cylindrical bond regions.
Commonly, the light sources used for curing these devices are “spot cure” systems. These systems consist of a small arc lamp, a reflector and a light guide. The arc is focused by the reflector onto the input surface of the light guide. Light is coupled into the light guide and transmitted to the output end. The output radiation pattern from the light guide is a circular “spot” projected onto a plane; the diameter of the spot increases with distance away from the light guide.
The light guide may be furcated. This divides the input optical power among the furcations. These branches are then located around the object to provide irradiation of the object from different directions in an effort to improve uniformity. Each branch produces a spot of light, just as the non-furcated light guide. Furthermore, the irradiance from each branch is 1/n of the non-furcated light guide output, where “n” is the number of furcations. This reduces the irradiance on the object by 1/n in order to improve uniformity. A typical light guide is either liquid filled or quartz fiber bundles.
During curing, the object temperature will increase with increasing optical energy absorbed by the irradiated components. Because the devices being cured are usually small and thin, the absorbed energy must be minimized to prevent thermal damage to the exposed components. Thus is it is very important to minimize the UV incidence and dose while meeting the requirements for curing the entire part. This is best achieved with uniformly applied UV light. A perfectly uniform light field will bring all areas to full cure at the same time, minimizing heat generated in the part.
Other known approaches involve UV flood curing systems in which UV light from the light source is spread over a large area, say 5 inches by 5 inches for example. However, the UV curing light is non-uniformly distributed over the treatment surface. That is, the UV curing light has the highest irradiance at the center of the treatment area and falls off moving toward the edge of the treatment area. Furthermore, the UV curing light is incident from only one direction (the location of the source) and so does not uniformly illuminate the side of the object that is away from the source. Known UV spot and flood light curing systems for curing medical components are available from many companies, such as Dymax Corporation of Torrington, Conn.
Another approach is known as a cure ring, for example, commercially available from Lumen Dynamics Group, Inc. (formerly Exfo, Inc.). A cure ring is an adapter that goes on the end of a light guide and converts the conical light guide output to an annular ring of inwardly directed light, much like a donut hanging by a thread, where the thread is the input light guide, the donut is the cure ring and the inner edge of the donut hole is the output light surface.
Some conventional systems attempt to maintain a constant exitance at the output of the light guide since the light source output deteriorates over time. For example, a detector measures the irradiance at a point near the input to the light guide. As the lamp output power degrades, the detected irradiance decreases as does the irradiance at the light guide input surface. The detected irradiance stays in fixed relation to the irradiance at the light guide input surface due to the system geometry. As the detected irradiance drops, a feedback control system causes the power coupled to the light guide input face to increase either by increasing the lamp power or by opening an aperture that otherwise reduces power coupled to the light guide.
What is needed is a system and related methods to reliably and repeatably treat objects with substantially uniform irradiation over multiple surfaces of the object while minimizing over-exposure of portions of the object. Preferably such systems should allow for easy object insertion and removal for treatment or curing.